The simplest version of calendar can be based on example provided with Tomcat installation JSP Examples->JSP 1.2 Examples->Calendar. Downfall is that you work across multiple pages from
-current month with year you can either

select next/previous month view

select a day of the month

you can go next/previous day

select time

set appointment on given time

However if you looking for something more compact you looking either to use custom tags or JavaScript